The present invention relates to a hybrid power unit which charges a power storage device on the basis of an electric power generated by distributing a part of a power output by a main power source to a rotation output shaft, and distributing the other portions to a generator, and transmits the power to the rotation output shaft via a transmission by an electric motor driven by one or both of the electric power of the generator and the electric power of the power storage device.
As a hybrid power unit, for example, as a hybrid power unit for a vehicle, there has been known an apparatus which distributes an output of an internal combustion engine to a generator and a rotation output shaft, and transmits a power from an electric motor to the rotation output shaft via a transmission (refer, for example, to Japanese Laid-Open Patent Publication No. 2004-203219).
In this hybrid power unit, in order to prevent a shift delay and a shift shock at a time of a power-off shift, a rotating speed of the electric motor is controlled so as to come to a target rotating speed at a time of the power-off shift.
As another hybrid power unit, it has been proposed that an apparatus for preventing a shock at a time of shifting by reducing the torque of the electric motor, in the case that the torque is transmitted to the rotation output shaft from the electric motor at a time of shifting (refer, for example, to Japanese Laid-Open Patent Publication No. 6-319210).
It is expected that the shock at a time of shifting under a wide-range operating state can be prevented by applying the shift shock prevention achieved by the torque reduction of the electric motor described in Japanese Laid-Open Patent Publication No. 6-319210 to the hybrid power unit described in Japanese Laid-Open Patent Publication No. 2004-203219.
However, there is a case that the power storage device temporarily storing the electric power generated by the generator is limited in charging. In other words, in the case that the power storage device is in a charged state equal to or more than a reference value, it is necessary to stop the charging for preventing an overcharge and protecting the power storage device. Further, even in the case that a charging capacity of the power storage device is lowered at a time of a low temperature, it is also necessary to stop the charging for protecting the power storage device.
In the hybrid power unit described in Japanese Laid-Open Patent Publication No. 2004-203219 in the case of applying the structure in Japanese Laid-Open Patent Publication No. 6-319210 thereto, since an electric power consumption by the electric motor is lowered by reducing the torque of the electric motor, the charging amount with respect to the power storage device is increased.
At this time, if the charging is limited as mentioned above, it is necessary to cope with the torque reduction of the electric motor caused by lowering the output of the internal combustion engine and the charging prevention caused by the power generation of the generator. In the case that the output of the internal combustion engine is lowered, it is necessary to restore the output of the internal combustion engine at the same time of dissolving the torque reduction of the electric motor before and after an end of the shift.
However, it takes a long time to restore the output of the internal combustion engine, and response delay in a vehicle drive disturbs a driver.
If the torque reduction of the electric motor is inhibited at a time of shifting for preventing such response delay, it is impossible to prevent the shift shock.